In production of wiring, electrodes, or various components of electrical and electronic devices, a photo lithography technique is widely used to transfer a desired pattern to a thin resist film on a substrate or board.
Recently, with the higher integration of substrate circuits, the need for higher resolution resist has increased. However, since high resolution resist usually includes a highly hydrophobic photo initiator, such photo initiator insoluble in alkaline solution is prone to precipitate and adhere to a resist developing apparatus. An operation of a resist developing apparatus in the presence of such precipitates, or deposited contaminant, may cause underdevelopment due to clogging of splay nozzles, or product defects such as open or short circuit. Such deposited contaminants should be removed regularly to maintain a developing efficiency and a good condition for resist developement.
Conventionally, physical cleaning methods are employed to remove deposited contaminants adhered to a resist developing apparatus. Such physical methods include scrubbing off deposited contaminants, or washing off deposited contaminants with a high pressure spray, after components of a resist developing apparatus are demounted. However, it is difficult to remove deposited contaminants in corners of a chamber or components, inside of a pipe, inside of spray nozzles and the like completely by such physical methods.
Chemical cleaning methods using a cleaning agent are also employed, without using physical cleaning methods. For example, in a method using concentrated acetic acid, a concentrated acetic acid solution is introduced to be circulated in a tank for reserving developing solution. Unlike physical cleaning methods, this chemical method does not require a step of disassembling components of a resist developing apparatus to be cleaned and makes it possible to remove contaminants in complicated portions of a resist developing apparatus. However, acetic acid is only used under carefully controlled and limited situations, since irritating smell of acetic acid exerts a bad influence on the operating condition and the environment outside an operating room, and also acetic acid is corrosive to a resist developing apparatus.
Another chemical method wherein a resist developing apparatus is cleaned stepwise with two kinds of liquid is also used, however, it is not as effective as the acetic acid method. Therefore, concentrated acetic acid is used to clean a resist developing apparatus in spite of its bad influence on the environment and a resist developing apparatus, or a substitute that is not as effective as acetic acid is used.